Note: Descriptions are shown in the official language in which they were submitted.
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Title of Invention:
"A truck mounted forklift"
.. Technical Field:
This invention relates to a truck mounted forklift. More specifically, this
invention relates
to a truck mounted forklift with an alternative linkage lifting assembly.
.. Backdround Art:
Truck mounted forklifts are a highly specialised type of lightweight forklift
truck that can
be mounted on the rear of a truck or trailer for transport to and from
customer's
premises. Once at the customer's premises, the truck mounted forklift can be
dismounted from the rear of the truck and used to load and unload goods from
the truck
or trailer before being remounted onto the rear of the truck or trailer for
transport to the
next customer's premises.
Out of necessity, the truck mounted forklifts must be lightweight as any
increase in truck
mounted forklift weight will correspond to a decrease in available haulage
capacity of the
truck or trailer about which it is mounted. Furthermore, the truck mounted
forklifts must
be compact in a fore and aft sense as the amount by which the truck mounted
forklift
may protrude from the rear of the carrying vehicle (commonly referred to as
"overhang")
is restricted by law in many jurisdictions. Furthermore, the greater the
overhang, the
greater the forces applied to the mounting. Increased forces necessitate
reinforcement of
these components which typically leads to increased weight which as described
before is
highly undesirable. An example of one such truck mounted forklift is that
disclosed in the
Applicant's own granted European Patent No. EP1711428. The present invention
is
concerned solely with this type of specialised lightweight forklift truck and
is to be
considered in light of the limitations of truck mounted forklifts. The present
invention is in
no way intended to relate to other types of forklift trucks such as the
commonplace
heavyweight counterbalanced forklift trucks that are not so restricted and do
not require
the same design considerations.
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Heretofore, some of the most common lifting assembly configurations used in
truck
mounted forklifts have been moving mast, static mast and telescopic boom
configurations. The moving mast and static mast implementations typically
comprise an
upright mast with a pantograph linkage or other mechanism to increase the
reach of the
forks carried on the mast. While each of these configurations has advantages,
each also
has a distinct problem with loading and unloading the top far side of a
container or
trailer. Due to the height of the pantograph arrangement, moving masts with
pantograph
sections cannot reach under the top of containers or trailers. Static mast
machines can
only reach the far side of a trailer if they can drive the front wheels under
the truck or
trailer which is not always possible. Furthermore, static mast machines
equipped with a
pantograph arrangement may also be prevented from reaching under the top of
the
trailer or container. Telescopic booms are obstructed by bottom near side
loads when
reaching top far side loads and the bottom near side loads must be moved prior
to the
top far side loads being accessed. In addition to the inconvenience, this can
also make
the trailer unstable as all the loads are on one side.
One useful type of truck mounted forklift is that disclosed in the Applicant's
own granted
European Patent No. EP1,531,141. Although EP1,531,141 provides a useful
alternative
for the consumer, there are however problems with the design of forklift
described
therein in that the lifting assembly of the forklift is relatively heavy and
bulky. This
decreases the load capacity of the carrying vehicle. Furthermore, the weight
distribution
of the lifting assembly of EP1,531,141 on the forklift is sub-optimal as the
weight is
relatively far forward on the forklift. This affects the maneuverability of
the forklift and
limits the lifting capacity of the forklift itself. In addition, the driver's
visibility is somewhat
impaired by the lifting assembly.
One proposed solution to the problems encountered with the known arrangements
of
lifting assemblies is a so-called linkage lifting assembly, as described in
the applicants
own published PCT patent application publication no. W02017/064313 entitled "A
truck
.. mounted forklift". The linkage lifting assemblies described therein,
particularly the triplex
linkage lift assembly, overcame many of the problems with the known
arrangements of
lifting assemblies however there are some problems with the duplex linkage
lifting
assembly having only two links described therein.
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First of all and perhaps most importantly, when the truck mounted forklift
with the duplex
linkage lifting assembly was mounted on the carrying vehicle (as illustrated
in Figure 27
of W02017/064313), the links protruded rearwardly from the carrying vehicle,
increasing
the overhang of the forklift truck substantially. As indicated above, this is
highly
undesirable. Secondly, the links would protrude rearwardly of the forklift in
various
modes of operation (see for example Figure 22 of W02017/064313) which is
undesirable from a health and safety point of view as well as preventing the
forklift from
operating in tight spaces. Thirdly, when picking up a load between the side
bars, the
links would protrude upwardly of the uppermost point of the forklift (see for
example
Figure 25 of W02017/064313) which is undesirable if the forklift is to be
operated in
areas of low clearance such as on the bed of a roofed trailer. The links could
obstruct the
forklift attempting to pick up a load. Finally, with the duplex linkage
lifting assembly, the
forklift follows a substantially arcuate path when being mounted or dismounted
onto a
vehicle. This arcuate path places a significant load onto the forks, requiring
reinforcement of the forks resulting in increased weight, which is highly
undesirable as
outlined above.
It is an object therefore of the present invention to provide a truck mounted
forklift that
overcomes at least some of the above-mentioned problems and that provides a
useful
choice for the consumer.
Summary of Invention:
According to the invention there is provided a truck mounted forklift for
mounting on the
rear of a vehicle, the truck mounted forklift comprising a u-shaped chassis
having a pair
of forwardly projecting side bars bridged by a rear crossbar, a wheel adjacent
the
forwardmost end of each of the side bars and a rear wheel mounted on the rear
cross
bar, a driver's station mounted to one side of the chassis, a motive power
unit mounted
on the other side of the chassis and a linkage lifting assembly mounted on the
chassis,
the linkage lifting assembly comprising:
a carriage slidably mountable on the chassis, the carriage being slidable
towards
and away from the rear crossbar and means to move the carriage back and forth
along the chassis; and
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a linkage, the linkage comprising:
an upright elongate first link connected at its proximal end to the carriage
by a
pivot joint;
an elongate second link connected at its proximal end to the distal end of the
first
link by a pivot joint, the elongate second link comprising a telescopic link
having a
plurality of link sections nested together;
a fork carriage connected to the distal end of the second link by a pivot
joint;
a plurality of link cylinders for actuating the links;
a telescoping cylinder for lengthening and shortening the telescopic second
link;
and
a tilt cylinder for actuating the fork carriage.
By having such a truck mounted forklift, the forklift overcomes the problems
of the known
moving mast, static mast and telescopic boom configurations with loading and
unloading
the top far side of a container or trailer. Advantageously, by providing the
linkage on a
carriage and a telescopic link as the second link, the linkage lifting
assembly can have
sufficient reach to access far side loads but also be sufficiently compact
that it will not
protrude rearwardly of the forklift, increasing the overhang of the forklift
when the forklift
is mounted on a carrying vehicle, or when the forklift is in use moving a
load.
Furthermore, by providing a telescopic link as the second link, the height of
the forklift
will not be increased to an extent that it would prevent operation of the
forklift in areas of
low clearance. Importantly, the telescopic link will permit the duplex linkage
lifting
assembly to be mounted and dismounted onto a carrying vehicle by operating the
telescopic link to move the forklift in a substantially vertical direction
rather than along an
arcuate path. This will facilitate mounting and dismounting of the forklift
and will obviate
the need to reinforce the tines or other equipment and increase the weight of
the forklift.
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In addition to the foregoing, there is a key advantage of the embodiment shown
over a
fixed boom assembly or the assembly shown in W02017/064313 in that the
configuration of lifting assembly described has a much-improved weight
distribution, due
to the mechanism being mounted on a moving carriage. Alternative boom designs
known in the art carry much of their weight to the rear of the forklift,
making the forklift
unstable, particularly when travelling unladen.
The embodiment of the invention also overcomes many of the limitations of
lifting
assemblies such as those described in EP1,531,141. The embodiment according to
the
invention is lighter that the lifting assembly of EP1,531,141 and will not
impede the
visibility of the driver to the same extent as the lifting assembly of
EP1,531,141.
Importantly, due to the fact that the pivot between the first link and second
link is
positioned further rearwardly on the forklift when compared to the lifting
assembly of
EP1,531,141, the configuration according to the invention will have improved
weight
distribution when lifting and improved lifting capacity.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
elongate second link is cranked intermediate its ends into a substantially L-
shaped
member such that with the linkage lifting assembly in a retracted
configuration, the spine
of the L-shaped member is directed substantially vertically and the arm of the
L-shaped
member is directed rearwardly from the uppermost part of the spine, and with
the linkage
lifting assembly in an extended configuration, the spine of the L-shaped
member is
directed forwardly and the arm of the L-shaped member is directed
substantially
vertically downwards from the rearwardmost part of the spine. This is seen as
a
particularly advantageous configuration of second link in that the link will
be able to more
easily clear near side loads. This will also enable a more compact mast to be
provided.
Furthermore, due to the L-shaped configuration, the lifting assembly will have
better lift
height relative to it's collapsed height when compared to lifting assemblies
such as those
described in EP1,531,141.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
elongate second link is cranked intermediate its ends into a substantially L-
shaped
member such that the arm and the spine of the L-shaped members are
substantially
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orthogonal with respect to each other. This is seen as particularly useful as
this will
provide greater height to the distal end of the second link as it pivots about
the pivot
point and will enable the first mast section to be more compact than would
otherwise be
the case.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
elongate first link is cranked intermediate its ends into a substantially
upside-down L-
shaped member such that the spine of the L-shaped member is directed
substantially
vertically and the arm of the L-shaped member is directed rearwardly from the
uppermost part of the spine.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
main link cylinder is connected at one of its ends to the second link and at
the other of its
ends to the carriage. It is envisaged that the main lift cylinder may be
provided by a pair
of lift cylinders.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
main link cylinder is connected at one of its ends to the second link and at
the other of its
ends to the first link. Again, it is envisaged that the main lift cylinder may
be provided by
a pair of lift cylinders.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
secondary link cylinder is connected at one its ends to the first link and at
the other of its
ends to the carriage.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
first link is raked backwards from the vertical. By raking the first link
backwards, the
clearance for the cylinder will be facilitated.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
first link is raked backwards at an angle of the order of 5 to 15 degrees from
the vertical.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
telescoping cylinder is located internal the second link.
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In one embodiment of the invention there is provided a truck mounted forklift
in which the
telescoping cylinder is located external the second link.
In one embodiment of the invention there is provided a truck mounted forklift
in which the
tilt mechanism cylinder is located internal the second link.
Brief Description of the Drawinds:
The invention will now be more clearly understood from the following
description of some
embodiments thereof given by way of example only with reference to the
accompanying
drawings, in which:-
Figures 1 (i) to (ix) illustrate truck mounted forklifts with lifting
assemblies known
in the art;
Figure 2 is a lifting assembly for a truck mounted forklift according to the
invention in a raised configuration;
Figure 3 is a lifting assembly for a truck mounted forklift according to the
invention in a lowered configuration;
Figures 4 to 7 inclusive are side views of a truck mounted forklift according
to the
invention in a variety of load positions; and
Figures 8 and 9 are side views of an alternative configuration of truck
mounted
forklift according to the invention.
Detailed Description of the Drawinds:
Referring to Figures 1 (i) to 1 (ix) inclusive, there are shown views of truck
mounted
forklifts with known lifting assemblies. Figures 1 (i) to 1 (iii) illustrate a
truck mounted
forklift 1 with a movable mast 3 having a pantograph linkage 5. Figures 1 (iv)
to 1 (vi)
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illustrate a truck mounted forklift 1 with a static mast 7 having a pantograph
linkage 5.
Figures 1 (vii) to 1 (ix) illustrate a truck mounted forklift with a
telescopic boom 9.
Referring specifically to Figures 1 (i) to 1 (iii), the truck mounted forklift
with a movable
mast is illustrated engaging a load 11 in a variety of positions on a carrying
vehicle 13. In
Figure 1 (i) the truck mounted forklift 1 is shown engaging a load 11 located
in the
bottom far side position of the carrying vehicle. The movable mast 3 is
positioned
forwards on the forklift 1 and the pantograph linkage 5 is fully extended. In
Figure 1 (ii)
the truck mounted forklift 1 is shown engaging a load 11 located in the top
near side
position of the carrying vehicle. It can be seen that there are no impediments
to the lifting
assembly engaging loads in these positions. In Figure 1 (iii) the truck
mounted forklift 1 is
shown attempting to engage a load in the top far side position on the carrying
vehicle. It
can be seen that the pantograph linkage comes into contact with the underside
of the
roof 15 of the carrying vehicle 13. Accordingly, this lifting assembly is
unable to engage
loads in the top far side position on the carrying vehicle.
Referring specifically to Figures 1 (iv) to 1 (vi), the truck mounted forklift
with a static
mast is illustrated engaging a load 11 in a variety of positions on a carrying
vehicle 13. In
Figure 1 (iv) the truck mounted forklift 1 is shown engaging a load 11 located
in the
bottom far side position of the carrying vehicle. The front wheels 17 of the
truck mounted
forklift 1 are positioned under the carrying vehicle 13. The static mast 7 is
in position on
the forklift 1 and the pantograph linkage 5 is fully extended. In Figure 1 (v)
the truck
mounted forklift 1 is shown engaging a load 11 located in the top far side
position of the
carrying vehicle 13. Again, the front wheels 17 are positioned under the
carrying vehicle.
It can be seen that the static mast 7 and the pantograph linkage 5 extend
significantly
upwards of the load 11 and may be obstructed by the roof of the trailer (not
shown). In
Figure 1 (vi) the truck mounted forklift 1 is shown attempting to engage a
load in the top
far side position on the carrying vehicle. It can be seen that the front
wheels 17 are not
positioned under the carrying vehicle 13. It is not uncommon for the wheels of
the
carrying vehicle to impede the progression of the front wheels 17 of the
forklift under the
carrying vehicle 13. Accordingly, in those circumstances, this lifting
assembly is unable
to engage loads in the top far side position on the carrying vehicle.
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Referring specifically to Figures 1 (vii) to 1 (ix), the truck mounted
forklift with a
telescopic boom is illustrated engaging a load 11 in a variety of positions on
a carrying
vehicle 13. In Figure 1 (vii) the truck mounted forklift 1 is shown engaging a
load 11
located in the bottom far side position of the carrying vehicle. The
telescopic boom 9 is
positioned forwards on the forklift 1 and is fully extended. In Figure 1
(viii) the truck
mounted forklift 1 is shown engaging a load 11 located in the top near side
position of
the carrying vehicle. It can be seen that there are no impediments to the
lifting assembly
engaging the load 11 in these positions. In Figure 1 (ix) the truck mounted
forklift is
shown attempting to engage a load in the top far side position on the carrying
vehicle. It
can be seen that the telescopic boom comes into contact with the bottom near
side load
on the carrying vehicle 13 at the point indicated by circle 19. Accordingly,
this lifting
assembly is often unable to engage loads in the top far side position on the
carrying
vehicle. In order to overcome this obstruction, the bottom nearside position
would have
to be unloaded and reloaded, thus increasing the time taken to unload the top
far side
position and potentially making the trailer unstable.
Referring now to Figures 2 and 3, there is shown a linkage lifting assembly
for a forklift
truck, indicated generally by the reference numeral 100. The linkage lifting
assembly 100
comprises a carriage 101 slidably mountable on a chassis of a forklift (not
shown), and a
linkage 103. The linkage 103 comprises an upright elongate first link 105
connected at
its proximal end to the carriage by a pivot joint 107 and an elongate second
link 109
connected at its proximal end to the distal end of the first link by a pivot
joint 111. The
elongate second link 109 comprises a telescopic link having a plurality of
link sections
109(a), 109(b) nested together. The elongate first link 105 is a fixed-length
link.
A fork carriage 113 is connected to the distal end of the second link 109 by a
pivot joint,
in this case provided by a tilt mechanism 110 actuated by a tilt mechanism
cylinder 112.
There are further provided a plurality of link cylinders 115, 117 for
actuating the links
109, 105 respectively, a telescoping cylinder 119 for lengthening and
shortening the
telescopic second link 109 and the tilt mechanism cylinder 112 for actuating
the fork
carriage about the pivot joint connecting the fork carriage to the distal end
of the second
link 109. In Figure 2, there is shown a carriage cylinder 120 for moving the
carriage
forwards and backwards along the forklift chassis.
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The elongate first link 105 and the elongate second link 109 are substantially
L-shaped.
The elongate first link 105 is cranked intermediate its ends into a
substantially upside-
down L-shaped member such that the spine of the L-shaped member is directed
substantially vertically, and the arm of the L-shaped member is directed
rearwardly from
the uppermost part of the spine. In addition, the elongate second link 109 is
also cranked
intermediate its ends into a substantially L-shaped member such that with the
linkage
lifting assembly 100 in a retracted configuration as shown in Figure 3, the
spine of the L-
shaped member is directed substantially vertically and the arm of the L-shaped
member
is directed rearwardly from the uppermost part of the spine, and with the
linkage lifting
assembly in an extended configuration as shown in Figure 2, the spine of the L-
shaped
member is directed forwardly and the arm of the L-shaped member is directed
substantially vertically downwards from the rearwardmost part of the spine.
Referring to Figures 4 and 5, there are shown views of a truck mounted
forklift, indicated
generally by the reference numeral 200, having the linkage lifting assembly
100 mounted
thereon. The truck mounted forklift 200 is configured for mounting on the rear
of a
carrying vehicle and comprises a u-shaped chassis 201 having a pair of
forwardly
projecting side bars 203 bridged by a rear crossbar 205. There is provided a
wheel 207
adjacent the forwardmost end of each of the side bars 203 and a rear wheel 209
mounted on the rear cross bar 205. There is further provided a driver's
station 211
mounted to one side of the chassis and a motive power unit (not shown) mounted
on the
other side of the chassis. The carriage 101 of the lifting assembly is
slidably mounted on
the side bars 203 of the chassis and is slidable towards and away from the
rear crossbar
205. There is provided means (not shown) to move the carriage back and forth
along the
chassis. In order to slidably mount the carriage on the side bars, the
carriage is provided
with rollers and the side bars are provided with complementary tracks for
reception of the
rollers. Referring specifically to Figure 4, the carriage is shown in its
forwardmost
position on the chassis with the tines 213 forward of the front wheels 207.
Referring
specifically to Figure 5, the carriage 101 is shown in its rearwardmost
position on the
chassis with the fork carriage rearward of the front wheels 207.
In both Figures 4 and 5, the tines are shown in a lowered position where they
may pick
up or drop off a load on the ground. It can be seen that the second link, the
telescopic
link, is practically vertical. It will be understood that with the second link
in this position,
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operation of the telescopic ram will cause vertical movement of the fork
carriage and the
tines. This is particularly advantageous for mounting and dismounting the
truck mounted
forklift.
Referring to Figure 6, the truck mounted forklift is shown engaging a top far
side load
215. The telescopic ram has been extended and the tines 213 are underneath the
load
215 and enable the load to be picked up. Importantly, due to the fact that a
pantograph
linkage is not required, it will be seen that the fork carriage will not
impact against the
roof (not shown) of the carrying vehicle. Furthermore, perhaps more
importantly, it can
be seen that the second link 109 will not impact against the lower near side
load 217 and
the lower near side load 217 will not have to be removed in order to allow
access to the
top far side load 215.
Referring to Figure 7, there is shown a truck mounted forklift 200 engaging a
bottom far
side load 219. It will be noted that this is achieved without the front wheels
207 of the
forklift being driven underneath the carrying vehicle 13. In this way, the
manoeuvrability
and operability of the forklift is improved. In order to achieve this, it is
envisaged that
there will be control circuitry to synchronize the operation of the tilt
cylinder 112 and the
link cylinders 115, 117. The control circuitry will be operable to ensure that
as the links
are raised or lowered, the tines 213 will remain in a fixed, substantially
parallel
relationship with the ground. Of course, the operator may provide an "offset"
degree of
forward or reverse tilt to the tines as required if picking up a load,
dropping off a load, or
carrying a load on the tines.
Referring now to Figures 8 and 9, there are shown side views of an alternative
configuration of truck mounted forklift, indicated generally by the reference
numeral 300,
and lifting assembly, indicated generally by the reference numeral 400, where
like parts
have been given the same reference numeral as before. It can be seen from
Figure 8
that the telescoping cylinder 119 is configured to be at least partially
extended in order to
place the tines 213 substantially at ground level. When the telescoping
cylinder 119 is
retracted, the tines 213 will be raised off the ground to the position shown
in Figure 9 so
that the tines may be used to engage tine pockets on a carrying vehicle for
mounting the
truck mounted forklift on the carrying vehicle.
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In use, in order to mount the truck mounted forklift onto the carrying
vehicle, lifting
assembly is retracted and the tines 213 are raised off the ground to the
position shown
in Figure 9. The forklift is then driven forwards to engage the tines 213 in
tine pockets
mounted on the chassis of the carrying vehicle (not shown). Once the tines 213
are
engaged in the tine pockets, the tines are forced downwardly by the operation
of the
telescoping cylinder. As the tines are fixed in position in the tine pockets,
this has the
effect of raising the forklift off the ground. Advantageously, the forklift is
raised and
lowered to and from the carrying vehicle practically vertically rather than
through an
arcuate movement and this reduces the forces exerted on the tines, allowing
lighter tines
to be used, increasing the carrying capacity for goods on the carrying
vehicle.
Various modifications could be made to the embodiments hereinbefore described
without departing from the scope of the appended claims or the spirit of the
invention.
For example, more than one link cylinder 115, 117 could be provided for the
second link
and the first link respectively. Additionally, the telescoping cylinder 119
could be located
internal the telescopic link sections however it could be external the
telescopic link
sections also, as illustrated in the drawings. In the embodiment shown, there
are only
two link sections 109(a), 109(b) in the telescopic link however more than two
link
sections in the telescopic link could be provided if desired.
In this specification the terms "comprise, comprises, comprised and
comprising" and the
terms "include, includes, included and including" are all deemed totally
interchangeable
and should be afforded the widest possible interpretation.
The invention is not limited to the embodiments hereinbefore described but may
be
varied in both construction and detail within the scope of the appended
claims.
